Urban effects of Chennai on sea breeze induced convection and precipitation

Doppler radar derived wind speed and direction profiles showed a well developed sea breeze circulation over the Chennai, India region on 28 June, 2003. Rainfall totals in excess of 100 mm resulted from convection along the sea breeze front. Inland propagation of the sea breeze front was observed in radar reflectivity imagery. High-resolution MM5 simulations were used to investigate the influence of Chennai urban land use on sea breeze initiated convection and precipitation. A comparison of observed and simulated 10m wind speed and direction over Chennai showed that the model was able to simulate the timing and strength of the sea breeze. Urban effects are shown to increase the near surface air temperature over Chennai by 3.0K during the early morning hours. The larger surface temperature gradient along the coast due to urban effects increased onshore flow by 4.0m s−1. Model sensitivity study revealed that precipitation totals were enhanced by 25mm over a large region 150 km west of Chennai due to urban effects. Deficiency in model physics related to night-time forecasts are addressed.

[1]  Raúl E. López,et al.  Spatial Patterns of Convection in South Florida , 1985 .

[2]  A. Bhatnagar,et al.  Unusual hail storms during May 2002 in Chennai and its suburbs – A study using data from a single Doppler Weather Radar , 2009 .

[3]  H. Pan,et al.  Nonlocal Boundary Layer Vertical Diffusion in a Medium-Range Forecast Model , 1996 .

[4]  J. Dudhia,et al.  Coupling an Advanced Land Surface–Hydrology Model with the Penn State–NCAR MM5 Modeling System. Part I: Model Implementation and Sensitivity , 2001 .

[5]  Zafer Boybeyi,et al.  A three-dimensional numerical sensitivity study of convection over the Florida peninsula , 1992 .

[6]  Roger A. Pielke,et al.  A Three-Dimensional Numerical Model of the Sea Breezes Over South Florida , 1974 .

[7]  U. C. Mohanty,et al.  Sea-breeze-initiated rainfall over the east coast of India during the Indian southwest monsoon , 2006 .

[8]  F. Vukovich,et al.  A Theoretical Study of the St. Louis Heat Island: Some Parameter Variations , 1978 .

[9]  Hiroshi Yoshik Ado.  Numerical study of the daytime urban effect and its interaction with the sea breeze , 1992 .

[10]  H. Yoshikado.  Interaction of the sea breeze with urban heat islands of different sizes and locations , 1994 .

[11]  Y. Ohashi,et al.  Local circulations developed in the vicinity of both coastal and inland urban areas : a numerical study with a mesoscale atmospheric model , 2002 .

[12]  R. McPherson,et al.  A Numerical Study of the Effect of a Coastal Irregularity on the Sea Breeze , 1970 .

[13]  S. Changnon,et al.  Precipitation Changes in Fall, Winter, and Spring Caused by St. Louis , 1991 .

[14]  Assessing Seasonal Transport and Deposition of Agricultural Emissions in Eastern North Carolina, U.S.A , 2003 .

[15]  F. Huff,et al.  Urban, Topographic and Diurnal Effects on Rainfall in the St. Louis Region , 1978 .

[16]  Hiromaru Hirakuchi,et al.  The effects of land-use alteration on the sea breeze and daytime heat island in the Tokyo metropolitan area , 2000 .

[17]  Stanley A. Changnon,et al.  METROMEX, a review and summary , 1981 .

[18]  G. Grell,et al.  A description of the fifth-generation Penn State/NCAR Mesoscale Model (MM5) , 1994 .

[19]  R. G. Semonin,et al.  Summary of Urban Effects on Clouds and Rain , 1981 .

[20]  D. Niyogi,et al.  Observational and Numerical Study on the Influence of Large-Scale Flow Direction and Coastline Shape on Sea-Breeze Evolution , 2004 .

[21]  J. Dudhia,et al.  Coupling an Advanced Land Surface–Hydrology Model with the Penn State–NCAR MM5 Modeling System. Part II: Preliminary Model Validation , 2001 .

[22]  S. Changnon,et al.  Rainfall Changes in Summer Caused by St. Louis , 1979, Science.

[23]  M. Hjelmfelt.  Numerical Simulation of the Effects of St. Louis on Mesoscale Boundary-Layer Airflow and Vertical Air Motion: Simulations of Urban vs Non-Urban Effects , 1982 .

[24]  Roger M. Wakimoto,et al.  Influence of the Synoptic-Scale Flow on Sea Breezes Observed during CaPE , 1997 .

[25]  R. Suresh.  Observation of Sea Breeze Front and its Induced Convection over Chennai in Southern Peninsular India Using Doppler Weather Radar , 2007 .